Regioselectivity of E2 reactions Section 8.7

8.7 Regioselectivity of E2 If there are multiple reactive sites or regions on a molecule, multiple products are possible In elimination reactions, there are often different β sites that could be deprotonated to yield different alkenes What is the relationship between the alkene products? Regioselectivity occurs when one constitutional product is formed predominantly over the other Zaitsev product Hofmann product Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e

8.7 Regioselectivity of E2 The identity of the base can affect the regioselesctivity Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e

8.7 Regioselectivity of E2 Why does the Zaitsev product predominate when a base that is NOT sterically hindered is used? Is the Zaitsev product kinetically favored, thermodynamically favored, or both? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e

8.7 Regioselectivity of E2 Why does a sterically hindered base favor the Hofmann product? Sterically hindered bases (sometimes called non-nucleophilic) are useful in many reactions Practice with SkillBuilder 8.5 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e